Multi-party telephone conferencing is in widespread use. However, one disadvantage of such conferencing is that all information within the conference is of the audio type, and no visual information is available. Another disadvantage is that the identity of a person speaking at any given time is not known to the others, except through recognition of the speaker's voice.
Thus, the following type of awkward situation frequently arises: if one participant wishes to comment on another participant's statements, the commentator, in general, cannot say, "I agree with Albert's position," because the commentator does not know whether Albert made the statements. The commentator generally uses a more stilted, and less friendly, phraseology, such as, "I agree with the last speaker," without naming that speaker.
An advancement over telephone conferencing is found in video conferencing, which adds video information to the audio conference. In a typical video conference, all parties view a common video image, and see video images of each other. When a participant speaks, the speaker can be readily identified, because the other participants see the speaker. The conferencing system can include sketching facilities, wherein a conference participant draws a sketch, and that sketch is reproduced on other computers.
However, video conferencing, in general, require high-bandwidth data channels, such as ISDN (Integrated Services Digital Network) service, communication satellite links, or an equivalent. Such channels are not in widespread use, and are far less available than ordinary telephone service. Thus, many people having access to telephone service cannot gain access to video conferencing.
In addition, high-bandwidth channels can be expensive. In 1998, one type of ISDN link imposes a fixed cost of about $50.00 per month, plus a per-minute usage charge. In addition to these costs, expensive equipment is required for video conferencing. Each participant requires (1) a video camera, (2) a microphone, (3) one or more expansion cards for a computer to digitize signals produced by the camera and microphone, (4) circuitry to interface with the high-bandwidth channel, and possibly other equipment.